In the case of converters, it is conventional that the actual value I_actual of the motor current can be measured, the current-sensing device being situated in the converter. The signals provided by the current-sensing device of the control electronics are initially supplied to a filter 1, e.g., a PT1 filter, as shown in FIG. 1. Therefore, microcontroller 2 is provided with filtered measuring signals, and interference signals become suppressible. The PT1 filter may take the form of a low-pass filter having a time constant of, e.g., 20 μs.
In the case of these converters, it may be that when long cables are used between the converter and the powered electric motor, and the capacitance of the cable produces recharging-current peaks that are too high. This is because the converters are operated in a pulse-width-modulated manner, and a change in voltage at the output of the converter produces large, short-term, charging-current peaks of this cable capacitance.